Apparatus for screening crushed ores or other materials.



No. 697,353. Patnted Apr. 8, I902.

W. McDERMOTT. APPARATUS FOR SCREENING cRuSHEn ORES OR OTHER MATERIALS.

(Application filed Mar. 22, 1901.

(No Model.)

' UNrTE STATES PATENT ()FFIE.

IVALTER MODERMOTT, OF LONDON, ENGLAND.

APPARATUS FOR SCREENING CRUSHED ORES OR OTHER MATERIALS.

SPECIFICATION forming part of Letters Patent No. 697,3 53, dated April 8, 1902.

Application filed March 22, 1901. Serial No. 52,366. (No model.)

To ctZZ whom, it may concern.- I

Be it known that I, WALTER MCDERMOTT, a subject of the King of England, residing at 43 Threadneedle street, in the city of London, England, have invented a certain new and useful Improvement in Apparatus for Screening Crushed Ores orother Materials, of which the following is a specification.

This invention relates to the screening or separating of crushed ore or other materials solely with regard to the size of the particles and irrespective of the specific gravity of same, and thus is in direct contrast with the Well-known forms of jigging-machines, in which the materials of the same size are separated by their different specific gravities, all as hereinafter more fully set forth.

The invention may be carried into practical use by aid of apparatus which in general appearance largely resembles a jig-machine, but which in reality is so modified in construction as to enable the desired result to be attained and the particles separated according to size with a much less expenditure of water than is customary in screening.

To clearly explain the present invention, reference is made to the accompanying drawings, in which Figure l is a plan view of apparatus in which a plunger is employed as in the ordinary jigging-machine. Fig. 2 is a sectional elevation of same on line X X. Fig. 3 is a section on line Y Y; Fig. 4, a similar view to Fig. 1, except that the screen is vibrated in lieu of the particles thereon being agitated by water pulsation; and Fig. 5 is a sectional elevation of same.

In the concentration of ores by water on various machines it is usual to classify the broken rock into Various sizes by means of screens for the purpose of treating the various classes or sizes separately in order to get the separation of heavy mineral from light waste. The usual system of screening is by revolving inclined cylindrical or conical screens; but as the water accompanying the crushed ore passes quickly through the screen it is necessary to add washing-jets of water from the outside or inside of the screens to wash the fine particles through the perforations, while the coarser particles are discharged from the end of-the cylinder. Where plain inclined shaking-screens are employed in place of cylinders, the operation equally requires extra spraying-jets of wash-Water.

Owing to the great wear and tear of the screens it is not found practicable to use these for fine material, as thin punched metal sheets or fine-wire-wove screens are rapidly destroyed. Consequently it is the custom in concentration-mills to substitute classification by upward-flowing currents of Water in pointed boxes for screening on material finer than about one-sixteenth inch and sometimes even one-eighth inch. The use of upward currents of water, however, does not classify like a screenintoequal-sized particles,butinto equal falling particles, so that an ore consisting of light rock containing a heavy mineral of higher specific gravity will yield under Water separation and in the'same com partment small particles of mineral and relatively large particles of rock, which is a disadvantage in subsequent treatment. Again, the volume of Water accompanying the material below onesixteenth-inch size, alreadylarge from its suecessive additions of wash-water sprayed on the larger-sized screens used for taking out the coarser particles, is greatly increased in passing over several pointed boxes with upward currents of water to separate the finer sizes, and hence the finest size of all (or slimes) is carried off in a great mass of water, involving difficulty in any treatment and necessarily causing great loss of fine mineral, coupled with a large consumption of water.

According to this invention the wear of screens is largely reduced and the necessity of using wash-water is practically abolished,

so that screening may be economically employed on much finer material than heretofore, and the losses and difficulties involved in excessive use of water may be avoided. This is accomplished by using an inclined screen submergedin water in a divided tank so arranged that all the muddy water entering with the crushed ore must pass through the screen into one compartment and not accompany the coarser particles, which drop from the end of the screen into a second compartment full of clear Water maintained at the same level as the muddy water in the first compartment.

In the drawings, 1 is a pointed tank with discharge for a regulated fiow of water and fine material at 2. The box 3, with inclined screen a forming its bottom, rests in the tank l, but is removable for the purpose of replacing the screen as required. At the lower end of the box 3 is an opening 5, just above the screen-surface and the full width of the latter. The screen terminates in a lip entering the second water-tank G, which is provided with a regulated discharge 7 at the bottom and a water-inlet supply 8. The tank 1 is divided longitudinally in its upper part by the partition 9, one side being occupied by the screen-box 3 and the other compartment being fitted with a loose-working plunger 10, operated by an eccentric 11, as in an ordinary jig-machine.

The operation of the apparatus is as follows: The tanks 1 and G are retained full of water to a point above the screen-surface. The crushed ore and water fiows into the upper end of screen-box 3 by launder 12. The discharge 2 is opened sufiiciently to maintain the water-level at the fixed point above the screen. This can be arranged an tomatically, if desired, by a float 16 in tank or compartment 6, attached to a lever 17, regulating the outflow-cock in pipe 2. The plunger 10 is set in operation, giving a rapid pulsating motion to the water in the screen-box through the screen-bottom, all the muddy water and finest particles of ore being compelled to pass through the screen and down to the discharge 2. The coarser particles of ore which cannot pass through the screen move down the inclined surface of thelatterbya series of rises and falls due to the pulsations of the water and discharge through the opening 5 into the compartment 6, where they fall to the bottom and run outwith a small stream of water by discharge 7. In order to prevent muddy water and fine sand from flowing into compartment 6 and also to prevent the addition of any further water to the ore than that in which it is carried, it is essential that the levels in tanks 1 and (i should be maintained substantially equal, as if this is not the case there will be more or less flow through opening 5. Theoretically, an absolute balance is desirable for the best results; but when treating ores containing very rich slimes a minute flow from compartment 0 to compartment 1 will prevent any chance of even the smallest quantity of slime passing outwith the coarser material, with resulting loss thereof. The effect of this arrangement and regulation is that all muddy water and sand finer than the holes of the screen is delivered in a steady stream at 2, while all the particles coarser than the holes in the screen flow off at 7 in a small stream of clear water.

Although in appearance the apparatus resembles at first glance a jig used in the concentration of ores, it is both in details and function entirely distinct from this wellknown machine, as will be seen. In a jig the function of the screen, which is placed level and not inclined, is to supportabed ot'heavier material than the Waste rock to be separated, and on this bed is maintained a layer of the particles of ore to be treated of a depth of several inches. There is no discharge of the whole of the muddy water and sand finer than the screen through the latter; but the muddy water flows off with the fine sand at the end of the screen-box over a partition which regu-' lates the depth of ore retained on the screen. The bed of heavy material retained on the screen prevents the small particles of lighter rock from passing down and through the screen. The function of the pulsation of the water in a jig is to lift and allow to fall the whole depth of material on the screen, so as to stratify the latter according to specific gravity of its component parts, keeping the light rock or waste at the top and forcing it over the end partition with the muddy water as fresh ore flows in and raises the level of the bed of particles, which by its motion keeps horizontal at the surface. The particles which work down are those having the greatest specific gravity, not the smallest size.

In this invention the use of the water pulsations is solely to keep the screen from clogging, and the same result may be attained by giving to the inclined screen 4 a shaking motion, as illustrated in Figs. 4 and 5, in which screen-box 3 is carried by supportingarms 13 and receives short rapid longitudinal vibrations from eccentric 11, and in this case a spring 14, attached to the screen-box and some fixed point, as the bracket 15, will prevent much of the knocking due to any wear of the eccentric. In the same manner a cylindrical revolving screen submerged in water can be utilized to effect a similarseparation.

It is of course not broadly new to employ one or more submerged screens to which a vibratory motion is imparted for separating ores or other materials; but so far as I am at present aware in all such apparatus the specific gravity of the particles has played an important part in elfecting the separation, in addition to which fresh water has been introduced into the slimes, so as to assist in separating the fine particles from the larger and heavier grains. One of the essential features of this invention is that no addition of water is made to that which already carries the finer particles of ore or slimes as they enter the machine, the action of the apparatus being such that the larger particles incapable of passing through the screen and irrespective of their specific gravity are removed from the slimes without the addition thereto of any further jet or wash-water.

What I claim is- 1. In a screening device, a main tank subdivided into reception and discharge chambers separated by a screen, the chamber below the screen being closed against inflow of water except through the screen, the upper chamber being provided with a restricted discharge-passage on a level with the upper surface of the screen and leading into a waterchamber, a water-supply for said water-chamber adapted to maintain a head of water therein substantially the same as that in the main tank, so as to prevent interflow, a discharge for the water-chamber, a separate discharge in the main tank for the slimes and water which have passed through the screen, and means for feeding the material under treatment into the chamber above the screen and for causing it to move thereon.

2. In a screening device, a main tank subdivided into reception and discharge chambers separated by a screen, the chamber below the screen being closed against'inflow of water except through the screen, the upper chamber being provided with a restricted discharge-passage on a level with the upper surfaceof the screen and leading into a waterchamber, a water-supply for said water-chamber adapted to maintain a headof water there-' :in substantially the same as that in the main tank, so as to prevent interflow, a discharge for the water-chamber, a separate discharge inthe main tank for the slimes and water which have passed through the screen, means for feeding thematerial under treatment into the chamber above the screen and. for causing it'to move thereon, and means for automatically discharging the slim es from beneath the screen.

3.-'In a screening" device, a main tank subdivided-into reception and discharge chambers separated by a screen, the chamberbe low the screen being closed againstinflowofwater except through the screen,the upper chamber being provided with a restricted discharge' passage on a .levelwith the upper surface of the screen and leading into a waterchamber, a water-supply for said water-chamber adaptedto maintain a head of water therein substantially the same as that in the main tank so as to prevent interflow, a discharge for the water-chamber, a separate discharge valve in the main tank and connections between the float and valve for automatically regulating the discharge of slimes.

4. In a screening device, a'main tank subdivided into reception and discharge chambers separated by a screen, the chamber below the screen being'closed against inflow of. water exceptthrough the screen, the upper chamber being provided with a restricted discharge-passage on a level withthe upper surface of the screen and leading into a waterchamber, a water-supply for said water-chamber adapted to maintain a head of water therein substantially the same as that in the main tank so as to prevent interflow, a discharge in saidcompartment as to impart a pulsating movement to therwater through the screen.

5. In a screeningdevice, a main tank subdivided into reception and discharge chambers separatedby a screen, the chamber below thescreen being closed against inflow of water except through the screen, the upper chamber being provided with a restricted discharge-passage on a level with the upper surface of the screen and leading into awaterchamber, a water-supply for said Water-chamber adapted to maintain a head of-water therein substantially the same as that in the main tank so as to. prevent interflow, a discharge for the water-chamber, a separate discharge in the main tank for the slimes and water which have passed through the screen and means for feeding the'materialunder treatment into the chamber above the screen, a second compartment communicating with the I chamber beneath the screen and a plunger so working in said compartment as to impart a pulsating movement to the Water through the screen, and means for automatically discharg ing the slimes which have passed through the screen.-. 7

6. Ina screening device, a maintank subdivided intoreception and discharge chamwater except through thescreen, the upper chamber being provided with a restricted discharge-passage on a level with the upper surface-of the screen and leading into a water.- chamber, a water-supply for saidwater-cham ber adapted'to maintain a head of-watertherein substantially the same as that in the main tank so as to prevent interflow, a discharge for the water-chamber, a separate discharge ICC in the. main tank forthe slimes and water 7 that have passed through the screen: and meansfor feeding the material under. treat- .ment into the chamber above the screen, a

second compartment communicating-With the chamber beneath the screen and a plunger so working in said compartment as to impart.-

a pulsating movement to the water through the screen, a float in the water-compartment,

a valve on the slime-discharge in the main.

tank and connections between the float and valve for automatically regulatingthe dis charge of slimes. V

In. testimony whereof I have hereunto set 1 my hand in the presence of two subscribing witnesses.

WVitnesses W.IJ. NoRvvooD, G. F. WARREN.

WALTER MoDERMo T'r-t 4 

